The present invention relates to a novel chlorine-free modified polyolefin resin composition with excellent adherence to nonpolar sheets, films and moldings of polypropylene, polyethylene, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, ethylene-vinyl acetate copolymer, etc. with excellent solvent solubility and compatibility with other resins, and with no tack after painting and drying.
Because of low price and many excellent properties such as moldability, chemical resistance, water resistance and electrical characteristics, polyolefins such as polypropylene and polyethylene are adopted widely in recent years as sheets, films and moldings, etc. Different from polar substrates such as polyurethane resin, polyamide resin, acrylic resin and polyester resin, however, polyolefin substrates are nonpolar and crystalline, leading to drawbacks of difficult paintability and adhesion.
So far, acid-modified polyolefins provided with various acid modifications to polyolefin or their chlorinated products have been used as paint additives, primers and adhesives, because of excellent adherence to said nonpolar substrates. While acid-modified chlorinated polyolefins are excellent in the adherence to substrates, solubility into solvent, compatibility with other resins, etc., the uses thereof have become to be kept at a distance from viewpoint of environmental problems in recent years.
On the other hand, while acid-modified chlorinated polyolefins have the adherence to nonpolar substrates, they have strong tack after painting and drying, thus arising problems of difficult winding of film after painting and handling of substrate, clinging of dirts, etc. Moreover, it has been known that, by using additives such as filler, the tack can be reduced, but remarkably decreased adherence cannot be avoided in this case, which posed a problem.
As another solution, a technique that alleviates the tack by blending with rigid tack-free resins has been known. But such rigid tack-free resins have poor solvent solubility as a rule, which posed a problem.
Furthermore, chlorine-free polyolefins are liable to have poorer solubility into solvent and compatibility with other resins compared with chlorinated ones, leading to restricted utilization toward the uses aforementioned. Based on the background as these, the development of a novel resin composition that combines excellent adherence to nonpolar substrates, solvent solubility, compatibility with other resins and low tackiness has been expected.
Conventionally, as the inventions that utilized ethylenic compound-maleic anhydride copolymer aiming at the adherence to polyolefin substrates, Japanese Unexamined Patent Publication Nos. Hei 6-256731, Hei 7-82328, Hei 7-97452, Hei 7-267692, Hei 8-34960, 2000-17121, etc. are mentioned. In these inventions, by using ethylenic compound-maleic anhydride copolymer and polyolefin or low-viscosity resin in combination, or adding additional modification, resins suitable for the moldings, hot melt adhesives, etc. were found.
However, since these resins did not necessitate the solubility into solvent and compatibility with other resins, they could not be utilized for primer, paint, ink binder, adhesive, etc. Moreover, when simply combining with low-viscosity resin, when conducting modification, or the like, problems of occurrence of tack in dried film, etc. also arose.
In the field at which the invention aims, therefore, there has been no precedent hitherto, in which a characteristic resin was developed, utilizing ethylenic compound-maleic anhydride copolymer.
The purpose of the invention lies in providing a novel chlorine-free modified polyolefin resin composition with excellent adherence to nonpolar resin moldings, with excellent solvent solubility and compatibility with other resins, and with no tack after painting and drying. As a result of diligent investigations for solving this subject, the inventors have found that this purpose can be accomplished only when unsaturated carboxylic acid derivative and/or its anhydride is graft polymerized at a particular rate onto a raw material with polyolefin resin mixed with ethylenic compound-unsaturated carboxylic acid copolymer at a particular rate, leading to the invention based on this knowledge.
According to the invention, following (1) through (6) are provided.
(1) A modified polyolefin resin composition obtainable by graft modifying a mixed resin comprising 40 to 99 parts by weight of polyolefin resin (A) and 1 to 60 parts by weight of ethylenic compound-unsaturated carboxylic acid copolymer (B) that contains 0.1 to 50% by weight of unsaturated carboxylic acid derivative, with unsaturated carboxylic acid derivative and/or its anhydride (C), the modified polyolefin resin composition having weight average molecular weight of 20,000 to 150,000 and the grafting weight of (C) being 0.1 to 20% by weight.
(2) A modified polyolefin composition obtainable by graft modifying a mixed resin comprising 40 to 99 parts by weight of polyolefin resin (A) and 1 to 60 parts by weight of ethylenic compound-unsaturated carboxylic acid copolymer (B) that contains 0.1 to 50% by weight of unsaturated carboxylic acid derivative, with unsaturated carboxylic acid derivative and/or its anhydride (C) and ethylenic unsaturated compound (D), the modified polyolefin resin composition having weight average molecular weight of 20,000 to 150,000 and the grafting weights of (C) and (D) being 0.1 to 20% by weight, respectively.
(3) An adhesive containing the modified polyolefin resin composition of (1) or (2).
(4) A primer containing the modified polyolefin resin composition of (1) or (2).
(5) A paint binder containing the modified polyolefin resin composition of (1) or (2).
(6) An ink binder containing the modified polyolefin resin composition of (1) or (2).
The nonpolar resins to become the adherends of the invention point to sheets, films and moldings of poly-propylene, polyethylene, ethylene-propylene copolymer and ethylene-vinyl acetate copolymer. Also, they include these substrates surface-treated with plasma, corona or the like.
The polyolefin resins (A) to be used in the invention are homo- or co-polymers of xcex1-olefins with number of carbon atoms of not less than 2 to not more than 20, preferably not less than 2 to not more than 6 such as ethylene, propylene, butene-1, pentene-1, hexene-1, heptene-1, octene-1 and 4-methyl-1-pentene, cyclopentene, cyclohexene chain or cyclic polyenes such as 1,4-hexadiene, 1,5-hexadiene, divinylbenzene, 1,3-cyclopentadiene, 1,3-cyclohexadiene and 5-vinyl-2-norbornene, or styrene, substituted styrene, etc.
The proportion of such monomer in polymer can be selected arbitrarily, but, in the case of polypropylene being the adherend, since the inventive modified polyolefin resin composition has the adherence to adherend, the proportion of propylene is preferable to be not less than 50% to not more than 98%. If under 50%, then the adherence to adherend is poor, and, if over 98%, the flexibility is insufficient. The usable molecular weight of polymer can be selected freely so as the weight average molecular weight of the modified polyolefin resin composition after addition of ethylenic compound-unsaturated carboxylic acid copolymer (B) and modification to become 20,000 to 150,000, For example, even a polymer with weight average molecular weight of over 150,000 becomes usable by the publicly known methods for adjusting the molecular weight to suitable range by degrading in the presence of heat or radical, and the like.
The ethylenic compound-unsaturated carboxylic acid copolymers (B) are ethylene-maleic anhyride copolymer, ethylene-propylene-maleic anhyride copolymer, ethylene-propylene-butene-maleic anhyride copolymer, ethylene-propylene-diene-maleic anhyride copolymer, copolymers of these with (meth)acrylic acid or its ester, or mixtures of at least two or more kinds selected from the group as described. Preferably, it is desirable to use ethylene-maleic anhyride copolymer or ethylene-acrylic ester-maleic anhyride copolymer. The content of unsaturated carboxylic acid in these copolymers is preferable to be 0.1 to 50% by weight, particularly 1 to 40% by weight. If under this range, then the solvent solubility is aggravated and, if above, the solvent transparency is aggravated, which is unpreferable. The usable molecular weight of polymer can be selected freely similarly to the case of (A). For example, even if the weight average molecular weight of polymer is under 20,000, it is only necessary for the molecular weight of the modified polyolefin resin composition to be within a range of 20,000 to 150,000 finally by increasing the molecular weight through crosslinking at the time of reaction or by properly selecting (A) to be used simultaneously.
Moreover, the proportion of (A) in the mixed resin of (A) and (B) is preferable to be 40 to 99% by weight, particularly 50 to 95% by weight. If under this range, then the solvent solubility and the adherence of modified polyolefin resin composition are aggravated, or decreased operativity, poor reaction, etc. due to increased viscosity at the time of reaction generate. If above this range, the tack occurs.
Unsaturated carboxylic acid derivatives and/or their anhydrides (C) are those modified with maleic acid, itaconic acid, citraconic acid, aconitic acid and their anhydrides, or (meth) acrylic acid or its ester. Moreover, preferably, it is desirable to use maleic anhydride or aconitic anhydride. The grafting weight of (C) in the modified polyolefin resin composition is preferable to become 0.1 to 20% by weight, particularly 1 to 10% by weight. If the grafting weight is under this range, then the solvent solubility and the adherence of modified polyolefin resin composition decrease. Also, if above inversely, much unreacted materials generate, which is unpreferable.
The ethylenic unsaturated compound (D) is at least one kind of compound selected from (meth)acrylic esters with number of carbon atoms of 1 to 12 such as glycidyl (meth)acrylate, cyclohexyl (meth)acrylate and ethyl acrylate, vinyl ethers such as butyl vinyl ether and cyclohexyl vinyl ether, styrenic compounds such as styrene, xcex1-methylstyrene, p-methylstyrene, t-butylstyrene, ethyl-styrene, cyanostyrene, aminostyrene, hydroxystyrene, vinyltoluene and N,N-diethylaminostyrene, and maleimides such as maleimide, N-phenylmaleimide and N-cyclohexylmaleimide. Preferably, it is desirable to use styrene. The grafting weight of (D) in the modified polyolefin resin composition is preferable to become 0.1 to 20% by weight, particularly 1 to 10% by weight. If the grafting weight is under this range, then the grafting weight of (C) in the modified polyolefin resin composition decreases, hence much unreacted materials of (C) tend to remain in the system. Also, if above inversely, the molecular weight increases and the solvent solubility are aggravated, which is unpreferable.
To the modified polyolefin resin composition of the invention, the stabilizer to adjust the stability of resin composition, the radical initiator to promote the reaction, and the like can be formulated further, depending on the purpose for use.
As the stabilizers, hydroquinone, benzoquinone, nitrosophenyl-hydroxy compound, etc. can be mentioned. The radical initiator can be selected appropriately from publicly known products, but, for example, it is preferable to use organic peroxides such as benzoyl peroxide, dicumyl peroxide, lauroyl peroxide, di-t-butyl peroxide and cumene hydroperoxide.
The grafting reaction by the use of said compounds to obtain the modified polyolefin resin composition can be conducted by publicly known methods. For example, the solution method wherein the mixed resin of (A) and (B) is dissolved into solvent such as toluene under heating and then (C) and (D) are added, the melt method wherein, to the mixed resin of (A) and (B) molten by employing Banbury mixer, kneader, extruder, etc., (C) and (D) are added, and the like are mentioned. As the addition method of (C) and (D), they may be added one by one or in a lump, and the order is also not minded.
The weight average molecular weight of modified polyolefin resin composition thus obtained is 20,000 to 150,000, preferably 30,000 to 120,000. If under 20,000, then the adherence to nonpolar substrates and the cohesion become poor, and, if over 150,000, the workability, solubility into solvent and compatibility with other resins decrease due to increased viscosity. The weight average molecular weight can be determined by means of publicly known methods, for example, GPC method, light scattering method, etc. Moreover, the identification of the reaction can be performed by alkali titration method, FT-IR, NMR, etc.
The inventive modified polyolefin resin composition can be used as an adhesive or primer for nonpolar substrates, paint binder resin and ink binder resin. It can be used in the forms adapted to uses such as solution, powder and sheet. Moreover, at that time, additives, for example, antioxidant, light stabilizer, ultraviolet absorber, pigment, dye, inorganic filler, etc. may be formulated, if need be.
In the applications to adhesive and ink binder resin, not only nonpolar substrates such as polyethylene and polypropylene, but also polar substrates such as polyester, polyurethane and polyamide are often used in combination. The inventive resin also has the adherence to such polar substrates, hence it is suitable also for said applications.
Similarly, when using as a binder resin for primer paint, it is excellent in the adherence to upper paint and clear coating, hence it is suitable also for said application.
When using as an ink binder, other resins such as urethane resin, epoxy resin, acrylic resin, phenol resin, alkyd resin, polyamide resin, polyimide resin, silicone resin and nitrocellulose may be blended, if need be.
When blending with other resins in these applications, it is required to use the inventive modified polyolefin resin composition in amounts of at least 5% or more by solids based on overall resin weight to maintain the adherence to nonpolar substrates.
Moreover, the inventive resin can also be used after curing reaction with epoxy, isocyanate, etc.
In following, the invention will be illustrated in more detail based on examples, but the invention is not confined thereto.